Research note / Cycle 010
Borrowing the whole instrument
A complete fixture is reserved while a covariance calculation keeps standard uncertainty distinct from acceptance limits.
Two channels make a difference
The surrogate-strip bench is intended to separate extension from motion in the grip and frame. Its corrected return subtracts a reference reading from the gauge reading. The earlier acceptance procedure retains a 25 micrometre displacement budget, a 6 micrometre return allowance and a 1000 micrometre sampled grid. None of those limits is relaxed here.
The GUM treatment of correlated inputs informs a new sensitivity calculation. For y=x1-x2, the combined variance is u1 squared plus u2 squared minus 2 rho u1 u2. With illustrative standard uncertainties of 4 and 3 micrometres, rho values -1, 0 and +1 give 7, 5 and 1 micrometres. These are authored inputs, not estimates from KIS-61 measurements.
A small number is not an acceptance
The sign matters because the measurand is a difference: positive correlation can reduce its uncertainty. This calculation does not show that the two installed channels are correlated, or that a common physical bias is harmless. Shared motion can cancel in a difference while remaining relevant to the absolute displacement being investigated.
Standard uncertainty describes dispersion under a stated model. It is not the earlier worst-case displacement allowance, a maximum observed return, or a material strength result. The next physical plan must retain raw channels and establish which environmental and reference terms are shared.
A new offer for the complete assembly
The December 15 stock reply offers KIS-61 on KB-2 together with its complete portable workshop fixture. This is a new offer after the earlier window closed. On December 16, Voss reserves the assembly for collection no earlier than December 21. The supplier still holds it; no delivery has occurred.
Keeping the offered assembly together avoids assuming its paperwork covers MRC-frame-01. Transport and installation can still change its behavior. The reservation therefore creates an equipment route, while installation review and independent stationary-reference custody remain prerequisites to a physical run. No strip is loaded during this cycle.
Results at a glance
| Authored correlation case | rho | Standard uncertainty (um) |
|---|---|---|
| negative_correlation | -1 | 7.0 |
| uncorrelated | 0 | 5.0 |
| positive_correlation | 1 | 1.0 |
External research and methods
- Evaluation of measurement data — Guide to the expression of uncertainty in measurement · Joint Committee for Guides in Metrology · JCGM 100:2008 (2008). Sections 5.1–5.2, especially 5.2.2.